This invention relates to an apparatus for guiding a weft yarn passing through a shed formed between warp yarns in a so-called jet loom.
In the past, in order to insert the weft yarn more smoothly into the shed formed between the upper and lower warp yarns, various designs for a weft yarn guiding apparatus have been produced. For example, a guiding apparatus has been known, which comprises a number of weft yarn guiding members arranged in spaced relationship in the direction of the weft insertion with apertures forming a continuous channel, through which the weft yarn is passed during the insertion thereof, each aperture having a large opening formed on the side of the reed, and a suitable number of sub-nozzles positioned in places along the channel so that their fluid outlets open into the channel. With this guiding apparatus, during the insertion of the weft yarn, the weft yarn is fed into the channel by a jet of fluid produced by a main nozzle positioned in alignment with the channel, while each of the sub-nozzles produces a jet of fluid acting on the weft yarn in cooperation with the main jet of fluid to make up the shortage of feed distance of the weft yarn, which would occur if the sub-nozzles were not employed, thus assisting the weft yarn in being fed smoothly through the channel.
However, in the afore-mentioned apparatus, because of the large opening formed in each of the weft guiding members, the fluid discharged from both the main and sub-nozzles is subject to escape from the openings, resulting in a greater consumption of the fluid. Moreover, because the jet of fluid produced by each sub-nozzle is directed toward the downstream weft guiding members at a certain angle with respect to the weft inserting direction so as to blow against the aperture surfaces of the downstream weft guiding members opposite to the large openings and thereafter is deflected at a large angle close to about 90.degree. with respect to the weft inserting direction, i.e., the weft yarn being fed through the apertures, the leading end of the weft yarn is apt to be entrained by the deflected flow of fluid, resulting in the disadvantage of passing out of the channel through the large openings during the insertion of the weft yarn. Such a disadvantage would be conspicuous especially when the leading end of the weft yarn deviates from the path of the main jet of fluid produced by the main nozzle. Also, it will be understood that the disadvantages of greater fluid consumption and unreliability of weft insertion would become a common phenomenon were a higher speed of the main and sub-fluid jets to be employed to increase the speed of weft insertion.
As a weft guiding apparatus which would appear to remove the disadvantages in the afore-mentioned weft guiding apparatus, a weft guiding apparatus with no sub-nozzles has been provided, which comprises a number of weft guiding members each having a substantially circular aperture with a small opening formed in the upper portion of each weft guiding member. However, this weft guiding apparatus has not been favourably used, because the above-discussed disadvantage of the unreliability of weft insertion has not yet been eliminated. Since the opening provided in each weft guiding member is of a slit-like shape greatly narrowed to such an extent that the weft yarn barely escapes therefrom, a relatively high differential pressure will develop between the inside and outside of the channel defined by the apertures when the fluid is discharged into the channel from the main nozzle. This causes a speed of fluid escaping or leaking through the slit-like opening to be greatly increased and the leading end of the weft yarn may be entrained by the fluid flow escaping at an increased speed, thus coming out of the channel through the slit-like opening. Therefore, it is understood that although the weft guiding apparatus with no sub-nozzles is considered to be reasonably improved in fluid consumption, it is still not able to provide sufficiently good reliability of weft insertion, which is the most important characteristic required in a weft guiding apparatus.
Then, in view of the above requirement, it has been attempted to provide each weft guiding member with an elastic tongue, which normally closes the inlet of the aperture's narrow opening, but, prior to the beating, opens the same by being deformed in terms of the inserted weft yarn to allow for the beating. Also, it has been attempted to provide each of the selected weft guiding members with a fluid passage, which has fluid outlets at positions circumferentially arranged around the aperture of the weft guiding member to supply a plurality of jets of fluid surrounding the fluid jet produced by the main nozzle. However, such attempts would involve additional disadvantages in that the weft guiding member is of a relatively complex construction and problems are encountered in the design of the elastic tongue and the fluid outlets, resulting in difficulties and increased costs in the manufacture thereof.
Therefore, it will be readily understood that a weft yarn guiding apparatus has been required, which enables weft insertion to be accomplished without failure at a reduced rate of fluid consumption, and which can be manufactured at a reduced cost.